3rd generation partnership project (3GPP) long term evolution (LTE) and institute of electrical and electronics engineers (IEEE) 802.16m have been developed as candidates of a next generation wireless communication system. The 802.16m standard has two aspects. One aspect is that the 802.16m is an amendment of the existing 802.16e standard in terms of continuity from the past. The other aspect is that the 802.16m is a standard for an international mobile telecommunication (IMT)-advanced system of a next generation in terms of continuity to the future. Therefore, the 802.16m standard needs to satisfy all requirements for the IMT-advanced system while maintaining backward compatibility with a mobile WiMAX system conforming to the 802.16e standard.
In general, a wireless communication system uses one bandwidth for data transmission. For example, a 2nd generation wireless communication system uses a bandwidth of 200 kHz˜1.25 MHz, and a 3rd generation wireless communication system uses a bandwidth of 5 MHz˜10 MHz. To support growing transmission capacity, the 3GPP LTE or the 802.16m has recently expanded its bandwidth to 20 MHz or higher. It may be necessary to increase the bandwidth to obtain high transmission capacity. However, if a large bandwidth is supported even when a service request level is low, it may cause significant power consumption.
Therefore, a multiple carrier system capable of transmitting and/or receiving broadband data by using a plurality of carriers has been introduced by defining a carrier having one bandwidth and a center frequency. By using one or more carriers, a narrowband and a broadband are both supported. For example, if one carrier corresponds to a bandwidth of 5 MHz, four carriers are used to support a bandwidth of up to 20 MHz.
If the multiple carrier system always uses all carriers, power may be excessively consumed in a mobile station. For example, if all carriers are always used by a mobile station having a service request level which is low enough to provide a service by using only one carrier, resource efficiency is decreased and a radio frequency (RF) front-end has an unnecessarily great load.
There is a need for a method capable of effectively operating multiple carriers according to a service request level.